Conventionally, as described in Japan Patent Laid-open number 2000-197374, a flow control valve used for a mass flow controller has the following arrangement: two inside flow channels are formed on a valve seat member wherein one end of one of the inside flow channels is in communication with an inflow channel and the other end thereof is in communication with an opening formed on a valve seated surface, and one end of the other inside flow channel is in communication with an outflow channel and the other end thereof is in communication with an opening formed on the valve seated surface. In other words, the conventional flow control valve has one opening for the fluid flowing in from an inflow channel and one opening for the fluid flowing out into an outflow channel. Then a diaphragm driven by an actuator such as a piezoelectric element is made to be seated on the valve seated surface or to be separated from the valve seated surface so that a flow is controlled.
It is necessary for the flow control valve having the above arrangement to lengthen a distance (hereinafter referred to as an “aperture”) between the valve seated surface and the seating surface in order to increase a flow of the fluid.
However, concerning a means to enlarge the aperture, there is a limit for a stroke width of the actuator such as the piezoelectric element as being a driving means of the diaphragm, and it is necessary to enlarge the actuator in order to increase the stroke width. Then there is a problem that the size and shape of the flow control valve becomes bulky.
In addition, concerning a means to enlarge a diameter of an inflow orifice and an outflow orifice of the flow control valve, the bigger the diameter is made, the bigger the area of the valve seated surface becomes. As a result there is a problem that the size and shape of the flow control valve becomes bulky.